FAA has ordered a 'Ground Stop' within 250 miles radius of the Lancaster high altitude control center. All flights out of LAX, ONT, etc, are being kept on the ground while flights already in the air are being allowed to land.
Flights may be released on a step by step basis, but huge delays are expected.
(Source: ABC 7 News Los Angeles.)
I'll bet that made those up in the air very happy!